Yavuz Demirhan is since a few years one of the most creative puzzledsigners; he tries to use always identical pieces for his designs, and that is just like a trademark for his designs; Chiasma ( greek. crossing) is a very intelligent burrlike unusual formed puzzle with 4 identical pieces to form in the end a crossing of these pieces

difficulty

the level of 16.4.6 makes it to a not so easy puzzle for advanced puzzlers